Re: Motion P1788/M007.01_NaI: Discussion period begins
> Date: Fri, 7 Aug 2009 16:28:56 +0200
> From: Vincent Lefevre <vincent@xxxxxxxxxx>
> To: stds-1788 <stds-1788@xxxxxxxxxxxxxxxxx>
> Subject: Re: Motion P1788/M007.01_NaI: Discussion period begins
>
> On 2009-08-07 09:32:23 +0200, Arnold Neumaier wrote:
> > Michel Hack schrieb:
> > >The "illegal construction" NaI is indeed the most important and general
> > >one. I believe however that there should also be one for "domain error".
> > >That is because in *some* uses of Interval Arithmetic, handling points
> > >outside a function's domain as if they did not exist is not desirable,
> > >whereas in other uses it is precisely the right thing to do. The Vienna
> > >proposal tries to deal with this by recording domain errors in a sticky
> > >flag and producing results according to the rule that points outside a
> > >function's domain don't contribute to the result set -- but that may lead
> > >to a lot of unnecessary calculations when NaI propagation would suffice.
> >
> > Unfortunately, domain mismatches cannot be accounted for by NaI, since
> > the flag should also be raised when evaluating sqrt([-1,1]) = [0,1].
>
> FYI, at the end of June / early July, Dan Zuras and I discussed
> privately on a proposal about sticky tags and what could be
> considered as different meanings for NaI. I disagreed with Dan's
> first proposal (which I found it too complex) but we eventually
> converged.
>
> --
> Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.org/>
> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
> Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)
I must admit that the idea I proposed to Vincent was based
on a quite different motivation & during the time that he &
I discussed it people on this list moved on in a different
direction.
I was going to try to repair the proposal to be in line with
the thinking you have all expressed but I was delayed some
weeks.
(The rest of my life got in the way. You know how that can
happen. :-)
During that time I came to realize that it was no longer
relevant. So I just dropped it.
I also involved John near the end but he hardly had time to
get involved before it was over.
I still appreciate Vincent's criticism, though. After all,
even a negative result guides us to the correct direction.
Dan